Polymeric membranes are useful in separating from water dispersed or emulsified oil, which has droplet sizes below 150 μm.
For example, ultrafiltration (UF) membranes, having a pore size of 0.01-0.1 μm, are used to treat oily industrial wastewater. See T. Bilstad and E. Espedal, Membrane Separation of Produced Water, Water Science and Technology 34 (9), 239-246 (1996). UF membranes have severe membrane fouling problems. See T. Bilstad and E. Espedal (1996); S. M. Santos and M. R. Wiesner (1997). Membrane fouling occurs when oil deposits onto a membrane surface or into its pores in a way that degrades the membrane's performance. It is a major obstacle to widespread application of UF membranes in treating oily wastewater.
Anti-fouling membranes are needed for effective and economical separation of oil from water.